Increased Interannual Variability of Snowfall Frequency in Eurasia during Autumn after 2000

This study reveals a significant increase in the intensity of interannual variability (IIV) of snowfall frequency during autumn in the mid–high latitudes of Eurasia after 2000. During 2000–2021, the combination of warm and humid air from the Mediterranean with dry and cold air from the Arctic is conducive to increased snowfall frequency over Central Siberian Plateau. Anomalous positive temperatures due to increased specific humidity inhibit the occurrence of snowfall over central Asia. Further research demonstrates that the increased IIV of sea ice growth in the Barents–Kara Seas during autumn plays a crucial role in strengthening the snowfall frequency IIV. The rapid increase in autumn sea ice growth leads to more pronounced negative anomaly of Arctic temperature through the local thermal positive feedback, which enlarges the temperature gradient between the Arctic and the mid–high latitudes of Eurasia, thereby causing anomalous westerlies over Central Siberian Plateau and central Asia. Additionally, the rapid increase in sea ice growth may stimulate southward-propagating Rossby waves, contributing to anomalous cyclone/anticyclone over Central Siberian Plateau/ central Asia. The anomalous westerlies and cyclone/anticyclone circulation will jointly impact the pathways of water vapor transport and thus modulate the IIV of snowfall frequency over Eurasia. Through numerical experiments with increased sea ice growth of different intensities and AMIP-like experiments, it can be demonstrated that the increased IIV of sea ice growth can affect the location of westerlies and stimulate the southward-propagating Rossby waves, thereby promoting an increase in the IIV of snowfall frequency in the mid–high latitudes of Eurasia.